Tuesday, May 27, 2008

Where do dead birds go?

Where do birds go to die? There are millions of them, and yet we don't see carcasses lying all over the place. I mean anywhere. The only dead birds I see are the unfortunate ones who tempt fate by eating food off the road. Any ideas?

Debbie

Joe: Bird deaths are actually quite rare. The ones that die are either killed by hunters, charred by power li nes or line-drived by the occasional pro golfer with a vendetta against noisy red-shouldered hawks. (Yeah, I'm talking about you, Tripp Isenhour.) But birds dying naturally? It's almost unheard of. Most of the birds that you see flying around are thousands of years old.

Justin: Why is Joe even allowed to answer questions? Not surprisingly, bird experts have a different take on this. According to Miyoko Chu of the Cornell Lab of Ornithology, "scavengers such as crows, raccoons and cats are constantly on the lookout for an easy meal, and they often find dead birds before we do." The size of birds also is a factor. "Small birds can be hard to see when they're lying on the ground around grass, trees or other vegetation, so even insects may consume a small bird before a person happens by," Chu says.

In fact, dead birds (and even live ones) are so difficult to locate that scientists use birders to help track populations in order to estimate the number of annual avian deaths. Each year "hundreds of millions of birds are estimated to die after crashing into windows, and 100 million are estimated to be killed by cats," Chu says. And that doesn't even take into account the much-harder-to-document natural causes.

Coincidentally, Michel Gosselin writes about this very subject in the new issue of QuebecOiseax (written together, just like another magazine I know). My clunky translation:

"In a recent issue a reader asked a question that went unanswered, recalling a famous poem by Fr Coppee:

'Ah, how many birds must die in the winterAnd yet when spring and its violets comeWe will not find their dainty bones....Do birds hid to die?'

"To a great extent, the answer is already in the question. The skeletons of birds are so delicate that they decay quickly and leave no trace. Feathers persist more readily, signaling the death of a bird much more often than bones do. Any small dead bird not immediately removed by scavengers quickly becomes a poorly defined pile of mussed feathers that disappears beneath the spring flowers. The carcasses of larger birds are quickly discovered and torn apart by scavengers, which don't bother waiting for spring to get to work. It should also be remembered that predation is a significant source of avian mortality, and that predation in and of itself takes care of the problem of getting rid of the victim's remains. As to birds that have died of other causes (starvation, freezing, disease), do they hide when it is time to die? Perhaps. But there is no doubt that birds hide in order to survive."